ZCZC SPCSWOMCD ALL
ACUS11 KWNS 211936 
SPC MCD 211936 
TXZ000-212200-

MESOSCALE DISCUSSION 0434
NWS STORM PREDICTION CENTER NORMAN OK
0236 PM CDT THU APR 21 2016

AREAS AFFECTED...PORTIONS OF SOUTHWEST TEXAS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 211936Z - 212200Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...VERY ISOLATED SVR TSTMS MAY OCCUR THIS AFTERNOON...THOUGH
WW ISSUANCE WILL NOT BE NEEDED.

DISCUSSION...VISIBLE SATELLITE IMAGERY AND MOSAIC RADAR LOOPS
INDICATE ISOLATED DEVELOPING CONVECTION WITHIN MULTIPLE REGIMES...
/1/ DIURNAL-HEATING-INVIGORATED OROGRAPHIC CIRCULATIONS AMIDST
BACKGROUND UPSLOPE FLOW OVER THE MOUNTAINS AROUND THE TX BIG BEND...
/2/ WEAK-CONVERGENCE ZONES MOVING SWD INTO RECYCLED MOISTURE
FEATURING DEWPOINTS IN THE MIDDLE/UPPER 50S SUBJECTED TO
INSOLATION/SFC HEATING...AND
/3/ A SEGMENT OF DIFFUSE OUTFLOW BOUNDARY NEAR THE RIO GRANDE RIVER.

CONTINUED DIABATIC SFC HEATING WILL ALLOW MLCINH TO ERODE...WITH THE
POTENTIAL FOR DEEPENING OF CONVECTION WITHIN THE AFOREMENTIONED
REGIMES. REFLECTIVITY RETURNS ARE ALREADY DEVELOPING IN ECTOR AND
BREWSTER COUNTIES...AND ISOLATED TSTMS WILL BE POSSIBLE ACROSS THE
AREA LATER THIS AFTERNOON. RELATIVELY STEEP MID-LEVEL LAPSE RATES
SUPPORTING 1000-2000 J/KG OF MLCAPE...COMBINED WITH 30-45 KT OF
EFFECTIVE BULK SHEAR...WILL SUPPORT A VERY ISOLATED SVR HAIL/WIND
RISK WITH MORE ORGANIZED TSTM STRUCTURES. HOWEVER...WEAK SFC
CONVERGENCE AND THE LACK OF SALIENT MID/UPPER-LEVEL PERTURBATIONS
FACILITATING DEEP/LARGE-SCALE ASCENT...SHOULD GREATLY MINIMIZE ANY
SVR COVERAGE.

..COHEN/GUYER.. 04/21/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...EWX...SJT...MAF...

LAT...LON   29050309 29740358 30810341 31390243 31140134 30380036
            29660013 29290080 29650146 29560248 29050309 

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